Water use efficiency is highest for

Answer: Option C

Water use efficiency is the ratio of water used in plant metabolism to water lost by the plant through transpiration.
Water use efficiency (WUE) is a measure of the amount of biomass produced per unit of water used by a plant. It is based on the concept introduced 100 years ago by Briggs and Shantz in 1913 showing a relationship between plant productivity and water use.
WUE is highest for the Finger millet (F. millet) as it adapted to hot and semi-arid conditions. It can withstand cultivation at altitudes over 2000 m above sea level, because of its high drought tolerance and the long storage time of the grains.